I’m controlling a fermentation fridge using a Spark + PI running brewblox. It controls well at fermentation temperatures (~20C) but the PID parameters are sub-optimal when I cold crash and at the resulting low temperatures (~1.5C). I’m planning to try to identify a set of PID parameters that work better for this but in the meantime, I manually adjust the I term to avoid large overshoot as the control loop settles after crashing. I realise this probably isn’t the best way of doing things but I hoped it was a workable “hack” that could be used in order to achieve acceptable control in the short term.
The problem I’m encountering is that the I term randomly changes by large amounts for no apparent reason. In the attached graph, the changes in I at ~16:56, 23:47 and 09:27 are manual changes, but the sudden drop to 0 at ~06:32 is not. It just spontaneously dropped to 0, without any intervention. Is this a bug, or is it an expected side effect of making manual changes to I?
Here’s a log: https://termbin.com/5gva